A ballistic two-dimensional-electron-gas Andreev interferometer

Abstract

We report the realization and investigation of a ballistic Andreev interferometer based on an InAs two dimensional electron gas coupled to a superconducting Nb loop. We observe strong magnetic modulations in the voltage drop across the device due to quasiparticle interference within the weak-link. The interferometer exhibits flux noise down to $\sim 80\, μΦ_0/\sqrt{\textrm{Hz}}$, and a robust behavior in temperature with voltage oscillations surviving up to $\sim7\,$K. Besides this remarkable performance, the device represents a crucial first step for the realization of a fully-tunable ballistic superconducting magnetometer and embodies a potential new platform for the investigation of Majorana bound states as well as non-local entanglement of Cooper pairs.

4+ pages, 4 color figures